The present invention relates to a process for producing polymer rubber, and also relates to oil extended polymer rubber. More specifically, the present invention relates to a process for producing polymer rubber, and oil extended polymer rubber, which rubbers have a high vinyl group content, a narrow molecular weight distribution, and more preferably a high molecular weight, and which rubbers are suitable particularly for tire use.
There is known a process for controlling a vinyl group content contained in butadiene copolymer rubber, which process comprises polymerizing butadiene in the presence of an ether such as tetrahydrofuran using an organolithium compound. However, the process has a problem that a large amount of tetrahydrofuran must be used in order to obtain rubber having a high vinyl group content.
JP-B 5-46365 discloses a process for controlling a vinyl group content by using two kinds of ethers. However, the process is not satisfactory from a viewpoint of obtaining efficiently butadiene copolymer rubber having a high vinyl group content. Moreover, according to the process, it is difficult to obtain butadiene copolymer rubber having a high vinyl group content, a high molecular weight, and a narrow molecular weight distribution, which rubber is suitable particularly for tire use.
An object of the present invention is to provide a process for producing polymer rubber, and oil extended polymer rubber, which rubbers have a high vinyl group content, a narrow molecular weight distribution, and more preferably a high molecular weight, and which rubbers are suitable particularly for tire use.
The present invention provides a process (the process being hereinafter referred to as xe2x80x9cProcess 1xe2x80x9d) for producing polymer rubber, which comprises the step of polymerizing a conjugated diene monomer or a combination of a conjugated diene monomer with an aromatic vinyl monomer in the presence of:
(1) an organolithium compound represented by the following formula (I), in which Rxe2x80x2 is an aliphatic or aromatic hydrocarbon group, which may contain a hetero atom, and X is an integer of 1 to 4,
Rxe2x80x2(Li)xxe2x80x83xe2x80x83(I)
(2) a solvent,
(3) tetrahydrofuran in an amount of 0.0106 to 0.1060% by weight, provided that an amount of the solvent is 100% by weight, and
(4) ethylene glycol diethyl ether in an amount of 0.02 to 0.30% by weight, provided that an amount of the solvent is 100% by weight,
wherein the polymer rubber satisfies the conditions:
(a) a vinyl group content in the polymer rubber is not less than 60% by weight, provided that an amount of a conjugated diene monomer unit in the polymer rubber is 100% by weight, and
(b) a Q value (Mw/Mn) of the polymer rubber is not more than 1.35.
Further, the present invention provides a process (the process being hereinafter referred to as xe2x80x9cProcess 2xe2x80x9d) for producing coupling-treated polymer rubber, which comprises the steps of:
(i) polymerizing a combination of a conjugated diene monomer with an aromatic vinyl monomer in the presence of:
(1) an organolithium compound represented by the above formula (I),
(2) a solvent,
(3) tetrahydrofuran in an amount of 0.0106 to 0.0742% by weight, provided that an amount of the solvent is 100% by weight, and
(4) ethylene glycol diethyl ether in an amount of 0.02 to 0.20% by weight, provided that an amount of the solvent is 100% by weight,
thereby obtaining polymer rubber satisfying the conditions:
(a) a vinyl group content in the polymer rubber is not less than 65% by weight, provided that an amount of a conjugated diene monomer unit in the polymer rubber is 100% by weight, and an aromatic vinyl monomer unit content in the polymer rubber is from 20 to 50% by weight, provided that an amount of the polymer rubber is 100% by weight, and
(b) a Q value (Mw/Mn) of the polymer rubber is not more than 1.30, and
(ii) reacting the above-obtained polymer rubber with a coupling agent,
wherein the coupling-treated polymer rubber has a Q value (Mw/Mn) of not more than 2.2 and Mw of not less than 600,000.
Furthermore, the present invention provides an oil extended polymer rubber, which comprises a conjugated diene monomer unit and an aromatic vinyl monomer unit, and satisfies the conditions:
(a) a vinyl group content in the oil extended polymer rubber is not less than 65% by weight, provided that an amount of a conjugated diene monomer unit in the oil extended polymer rubber is 100% by weight, and an aromatic vinyl monomer unit content in the oil extended polymer rubber is from 25 to 40% by weight, provided that an amount of a polymer rubber contained in the oil extended polymer rubber is 100% by weight,
(b) a Q value (Mw/Mn) of the polymer rubber contained in the oil extended polymer rubber is not more than 2.1, and Mw of the polymer rubber is not less than 1,100,000, and
(c) an oil content in the oil extended polymer rubber is not less than 40 phr.
Still further, the present invention provides a process (the process being hereinafter referred to as xe2x80x9cProcess 3xe2x80x9d) for producing oil extended polymer rubber, which comprises the steps of:
(i) polymerizing a combination of a conjugated diene monomer with an aromatic vinyl monomer in the presence of:
(1) an organolithium compound represented by the above formula (I),
(2) a solvent,
(3) tetrahydrofuran in an amount of 0.0106 to 0.0742% by weight, provided that an amount of the solvent is 100% by weight, and
(4) ethylene glycol diethyl ether in an amount of 0.02 to 0.20% by weight, provided that an amount of the solvent is 100% by weight,
thereby obtaining polymer rubber satisfying the conditions:
(a) a vinyl group content in the polymer rubber is not less than 65% by weight, provided that an amount of a conjugated diene monomer unit in the polymer rubber is 100% by weight, and an aromatic vinyl monomer unit content in the polymer rubber is from 25 to 40% by weight, provided that an amount of the polymer rubber is 100% by weight, and
(b) a Q value (Mw/Mn) of the polymer rubber is not more than 1.30,
(ii) reacting the above-obtained polymer rubber with a coupling agent to obtain a coupling-treated polymer rubber having a Q value (Mw/Mn) of not more than 2.1 and Mw of not less than 1,100,000, and
(iii) mixing the above-obtained coupling-treated polymer rubber with an oil,
wherein the oil extended polymer rubber has an oil content of not less than 30 phr based on 100 parts by weight of the coupling-treated polymer rubber.
In the above, a monomer unit such as xe2x80x9cconjugated diene monomer unitxe2x80x9d and xe2x80x9caromatic vinyl monomer unitxe2x80x9d means a polymerized monomer unit.